[RCaffin]

Isn't it wonderful what a tin of black paint can do?
Yeah - that is looking rather elegant now.
Smooth.

Cheers
Roger

[shedbob]

Your machine is looking very nice, professional.If I estimate its size correctly it fits within a 500mm cube.Nice and compact but strong.
How did you resolve the lack of smoothness (rail alignment?) in z/x axis?

[turpija]

yes it's a 500mm cube

for rails i've resurfaced aluminum on which i'll bolt rails to ... but as i've measured about 0,1mm "sag" in the middle of surface, i've drawn the oposite curve and let the cnc do the work again ... it's much more flat now, hard to measure cause i don't have adequate straight edge, but with plastic fishing string and light it looks nice

smoothnes is not an issue, but i've anticipated not as much resistance on linear sliders (it's about 0,8kg force to push single one), however with little or no grease, when i applied more grease it seems to goes much easier ...
but then again, the ballscrews have also a decent amount of resistance ... that's what low (or no) backlash fells like i guess

[ger21]

Do you have this in a temperature controlled environment? Most people use steel inserts. If it gets too cold, I wonder if the aluminum will shrink enough to pull away from the EG?
In my garage, I can see temperature changes from -5°C to 30°C.

[turpija]

interesting point ...
i've used aluminium because i could machine it with my own cnc ...

during last period it was cold here, and possibly hit a 0 inside workshop, however i haven't monitor, or notice any change, between alu and eg

now i'm thinking what could be the best way to periodically check for and deformation caused by temperature, and at what points of machine ... if you have any idea, please do tell, it's interesting subject, especially because i want to machine fairly small parts with (ofcourse) tight tolerances

[RCaffin]

> In my garage, I can see temperature changes from -5°C to 30°C.

I'll raise you +5 C...

Yeah - could be a problem.

Cheers

[DYSEQTA]

Thanks for the detailed pics, really nice to be able to follow this process closely!
You make it look easy

Could you share what mix you are using? It seems to be a mix of say 5 mm pebbles and sand and (estimate) 7%-10 or so epoxy?

Just re-iterating this request as I am very interested as well and didn't see a response from turpija. I would also like to know more information in general about the epoxy-granite mix you have used and the mix process. Did you use vibration or vacuum or maybe a chemical additive to de-aerate? The more information the better as your results look fantastic.

[DYSEQTA]

Just re-iterating this request as I am very interested as well and didn't see a response from turpija. I would also like to know more information in general about the epoxy-granite mix you have used and the mix process. Did you use vibration or vacuum or maybe a chemical additive to de-aerate? The more information the better as your results look fantastic.

OK found turpija describing his mix here: http://www.cnczone.com/forums/epoxy-...52422-cnc.html

[shedbob]

Calculating the difference in dimensions using expansion coefficient.

Expansion figure for aluminium is 24 micrometres/metre/degree Celsius. Steel and eg both about half this.
So for 500mm length of eg undergoing a 15 degree temperature change the change in length will be
.5x(12x10e-6)x15=.09mm (90 microns or .0035in)
Shrinkage or expansion.Phew,thats enough maths for this year.

If thats a problem you need to control the temperature of the machine,what the pros do.It may help to build
an insulated enclosure using fibreglass insulation and a shrouded heater(so no direct radiation-to
create a differential expansion problem)and fan to circulate. Controlled with a domestic thermostat.
Its not going to take a lot of heat imo 10-20 watts might be enough,a power resistor or two maybe.
So the power bill shouldn't be huge.There is a fire risk of course as it would be unattended(metal enclosure).
The material heat properties will work to your advantage.It holds a lot of heat and heats or cools slowly so
any temperature changes from door opening during use wont have much effect.

[RCaffin]

Thread small bore copper tubes through the EG during casrting, and then thread wire out of an old electric blanket through the tubes. Might get away with running several lengths in parallel off 24 V for instance. You can buy qite cheap thermostats to control this.

Cheers
Roger

[turpija]

interesting calculations, but i think i'll have to live with "deformed" cnc

and to be on topic ...

cnc is currently - everywhere



but i hope to get it to single location soon

[RCaffin]

Just out of curiosity - how are you moving the bits around?
And what are you going to sit it on?

Me, I used a 2-ton chain hoist! And I needed it.

I note the limit switches on the gantry. To be sure, they are needed, but i woud have mounted them at right angles so they could not act as buffer-stops. If you overshoot and ram them, it could be expensive. Hum? (Yes, I have run into the hard end-stops a few times myself. Big clunk.)

Cheers
Roger

[A_Camera]

Hi turpija,

Very nice and interesting design. Looks very stable and vibration free and in fact, similar to the one I am working on in terms of work table area, except that I do it all in aluminum, so mine will not look as good as yours, mine is just a typical DIY CNC. I like your design a lot more than mine, but knowing I could never copy or make anything similar, I am not even dreaming about it. Anyway, nice work you have done and I hope to see the final and working CNC as well. Good luck.

By the way, what is the total weight so far? Mine is about 40kg, and as I said, mine is aluminum, so I think the 100kg you originally estimated should be well under reality with motors and everything else added. OK, in my case I also included the control box with power supply and everything else, which is built on top of the frame, so that adds to weight, but in your case, all that concrete plus the aluminum and steel parts and the motors weight also a bit...

[turpija]

2 RCaffin: i move it by hand at the moment, it's 40 and 30kg just epoxy pieces + few kilos of accessories attached, it would be manageable to move it around in two pieces when fully equiped, but i'll probably need two more hands
and with limit switches i agree, it's far from ideal position, but as i'm not using actual hard stops, and machine will be moving at 25-30mm/sek rapids it shouldn't be catastrophical scenario even if i hit em (which in theory shouldn't happen, soft limits and all that..)

2 A_Camera: 100kg will probalby be exceeded by small amount, i'll try to weight it when assembled somehow
i already have some interesting projects to test it's capabilities, so be sure to check for some youtube action

[RCaffin]

> it shouldn't be catastrophical scenario even if i hit em
You could rotate them 90 degrees maybe? Off to one side.
Or maybe anchor them down to the frame with nylon bolts. If they get hit, the nylon shears off.

Keep posting photos!

Cheers
Roger

[turpija]

Almost there ...

[RCaffin]

Hum ... progress.
Looks as though you have separated the two Y-axis rails a bit more? At first they seemed to me to be a bit close.
Gutsy looking motors too.
What revs on the spindle?

Cheers
Roger

[shedbob]

I am almost certain this will be the first machine constructed of eg on this forum.So congratulations will be due soon.Looking forward to the video.

[turpija]

some brass milling

[shedbob]

Congratulations on the successful completion of your eg mill.This is a build which I am sure has interested many people.Its of a size that many of us would find very useful and judging from other comments others (like myself) would like to emulate.You have shown us what can be accomplished without access to a well equipped workshop. Thank you for taking the time to document it for us.

Is there anything you would have done differently looking back at the build process?A picture of the completed machine would be nice.